1. Field of the Invention
The present invention relates to a method for controlling an interactive window-based user interface with at least two overlapping display and control windows.
2. Description of the Related Art
In the operation of computer systems, the window technique has gained wide popularity. The following definition of a window is given in Lexikon der Informatik und Datenverarbeitung [Dictionary of Information Systems and Data Processing], 3rd edition, R. Oldenbourg Verlag [Publishers], Munich, 1991, page 303: “A usually rectangular area on the display screen of a data terminal which can be regarded as an independent (virtual) display. With the help of windows various information units can be displayed and manipulated selectively at the same time.”
One problem that occurs repeatedly in practice is when several windows are displayed on the user interface of a computer monitor and partially overlap. There is thus a virtual stratification of windows arranged more or less one on top of the other. Only the contents of the window on top, i.e., the currently active window, are completely visible and accessible for operating control objects contained in that window, for example. The windows behind that window more or less, i.e., the windows not currently active, are partially or even completely covered by the active window and thus are at least not completely visible.
When using a computer system in an office environment, this problem is usually solved by the fact that the respective operator switches constantly between the opened windows displayed on the user interface. However, when a computer system is used in an industrial environment for observing and influencing industrial technical equipment, complete or partial coverage of the contents of the display of windows may be problematical, e.g., for safety reasons.
Technical equipment may be controlled and operated with the help of digital programmable devices, which may frequently also constitute an automation system and/or be part of such a system. Technical equipment is understood to refer to all types of technical devices and systems in an individual arrangement as well as in an arrangement in which a field bus, for example, provides technical data networking. Thus, technical equipment is understood to include individual production facilities as part of an industrial application, e.g., drives, machining equipment, etc. However, an entire production plant may also be regarded as technical equipment. Under some circumstances, an entire technical process, e.g., in a chemical plant, a manufacturing plant or a processing plant will be carried out with locally distributed production facilities. The scope of functions of programmable devices used for managing technical equipment is constantly increasing. In addition to decentralization of production facilities of such a device and their networking via bus systems, operability of the devices is becoming increasingly important. Distributed automation systems in particular may have special devices which form the interface between a user and the automation system.
Such devices are generally known as human machine interface (HMI) devices. In addition, it has become customary to refer to this class equipment as devices for “operator control and monitoring” of technical equipment, abbreviated as “control and monitoring devices.” These devices which are more or less upstream from the actual devices for direct control of technical equipment have an increasing functionality. A survey of the scope of function of HMI devices can be obtained, for example, by inspecting Internet displays of Siemens A G, Automation and Drives Division at http://www.ad.siemens.de/simatic/html—76/intro/hmi.htm or http://www.ad.siemens.de/hmi/html—00/index.htm. Furthermore, by activation of a conventional Internet search machine such as GOOGLE at the address http://www.google.de, an abundance of product instructions for HMI devices and systems can be found by entering a search query such as “human-machine interface.” The term HMI device is to be understood as an umbrella term including all components belonging to this group of devices, e.g., operator panels, frequently also abbreviated as OP.HMI devices have an increasing functionality and assume functions (e.g., in a networked automation system) which can generally be regarded as preprocessing and post-processing of data of the technical facility to be controlled. This does not just relieve the load on a central control unit, e.g., a programmable controller. Instead, an HMI device may permit functions which improve the user-friendliness, quality and safety of an operation by an operator, e.g., providing an overview of the equipment to be operated and error-free operations.
Thus an HMI device generates at least an interactive overview display or process image of the technical equipment to be operated. This permits first a pre-selection of operator actions to convert the equipment to the desired state. On the other hand, however, targeted display of reactions of the technical equipment is also possible, usually in the form of measured values and messages. This permits reliable observation of the status of the technical installation. Trouble messages which signal an unwanted state of the equipment and usually result in targeted input of operator actions by an operator into the HMI device assume a special position. With these, the trouble incident in the technical equipment which has generated the trouble message is to be influenced in such a way that the technical equipment is returned to a desired state again as soon as possible.
In a window-based user interface, problems may thus occur due to the fact that important window contents are concealed by currently active windows. For example, if a window in an HMI device contains an important trouble message of technical equipment, problems may occur due to the fact that this window is covered at least temporarily by another active window. For example, a person may perform a normal operating action, e.g., adapted to the setpoint for a process parameter.
German Patent DE 37 07 490 describes an arrangement for simultaneously displaying several images on the display screen of a monitor. An operator element is provided here so that the size and position of the images on the screen are adjustable. To this end, a window adjustment mark is displayed on the boundary lines of adjacent windows and is displaceable by the operator, with the boundary lines also being shifted. The detail displayed in a window can thus be adjusted manually in this way.